JP2015098385A - Sheet conveying apparatus and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a discharge roller 202 and slave rollers 204, 207 from being deflected in the transportation direction of a sheet S when the discharge roller 202 rotates forward and backward, relating to a triple roller configuration (a configuration in which two slave rollers 204, 207 are arranged to face discharge roller 202).SOLUTION: In a cross section vertical to the axial direction of the drive roller 202, a rotational center of the discharge roller 202 is provided at a position other than on a straight line connecting the rotational center of the discharge slave roller 204 with the rotational center of the both-sided slave roller 207. Further, the discharge roller 202 which receives a force from the both-sided slave roller 207 and the discharge slave roller 204 is pressed with a discharge roller presser 211.

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus.

  Image forming apparatuses such as copiers, printers, and facsimiles are required to be smaller and to be faster to print on both sides of a sheet.

  When printing (image formation) on both sides of a sheet, a roller that nips the sheet printed on one side is reversely rotated to convey the sheet to the duplex conveyance path. In general, a method of printing on a surface where printing is not performed by conveying the sheet to a transfer unit or a fixing unit in a state where the sheet is reversed is generally used. At this time, there are two general types of rollers that rotate in reverse, that is, a roller that is provided on a discharge path when a single-sided sheet is passed, and a roller that is provided only on a conveyance path that is used only during reversal. However, in the former case, the rollers are reversed and the next sheet cannot be conveyed until the sheet passes through the nip, which is disadvantageous for speeding up. In the latter case, two roller pairs must be installed, which is disadvantageous for downsizing.

  Therefore, in the image forming apparatus described in Patent Document 1, two driven rollers are opposed to one discharge roller (so-called triple roller configuration), thereby creating two nips and achieving both high speed and downsizing. I am letting.

Japanese Patent Laid-Open No. 2000-26002

  However, in the configuration described in Patent Document 1, since the rotation center of the triple roller (the driving roller and the two driven rollers) is arranged on one straight line, when the driving roller performs forward rotation and reverse rotation, The direction of the force may change, and the driving roller and the driven roller may sway in the sheet conveyance direction or the vertical direction. Then, due to the occurrence of roller runout, the conveyance of the sheet becomes unstable, and in some cases, jamming may occur.

  The present invention is provided with a driving roller that can be rotated forward and backward by receiving a driving force from a driving source, and a first roller that is provided at a position facing the driving roller and that rotates following the driving roller. A driven roller, a second driven roller which is provided at a position opposite to the driving roller and rotates in accordance with the rotation of the driving roller, and biases the first driven roller toward the driving roller. A first urging portion; a second urging portion that urges the second driven roller toward the driving roller; and a rotation of the driving roller in a cross section perpendicular to the rotation axis direction of the driving roller. The center is provided at a position other than a straight line connecting the rotation center of the first driven roller and the rotation center of the second driven roller, and is urged by the first urging portion. Energized by the roller and the second energizing part A sheet conveying apparatus characterized by having a pressing portion which is the driving roller which receives a force from the second driven roller presses the driving roller so as not to move.

  According to the present invention, the vibration of the driving roller and the two driven rollers can be reduced.

Sectional drawing of the image forming apparatus 100 to which 1st Embodiment was applied. The perspective view of the inversion part 20 of 1st Embodiment. Sectional drawing which shows the relationship of the force of the discharge roller 202, the discharge driven roller 204, and the double-side driven roller 207 The perspective view of the inversion part 20 of 1st Embodiment. Sectional drawing of the inversion part 20 of 1st Embodiment Sectional drawing of the inversion part 20 of 1st Embodiment Sectional drawing which shows the behavior of the sheet | seat S in 1st Embodiment The figure which shows the modification of 1st Embodiment. Block diagram of the first embodiment

<First Embodiment>
(Description of overall configuration of image forming apparatus 100)
Hereinafter, a first embodiment to which the present invention is applied will be described with reference to the drawings.

  First, the configuration of the image forming apparatus 100 that is a laser beam printer and the image forming process will be described with reference to FIG.

  FIG. 1 is a schematic sectional view of the image forming apparatus 100. As shown in FIG. 1, the image forming apparatus 100 includes an image forming unit 101, a feeding unit 102, a laser scanner unit 104, a fixing unit 103, a reversing unit 20, and a discharge tray (stacking unit) 106.

  The feeding unit 102 includes a feeding cassette 21, a separation pad 22, and a feeding roller 23, and the stacked sheets S are fed by the feeding roller 23, and are separated and sent one by one by the separation pad 22. Thereafter, the sheet S is conveyed further downstream by a pair of feeding and conveying rollers formed by a feeding and conveying roller 24 and a feeding and conveying roller 25 provided on the downstream side in the conveying direction. Further, the feeding unit 102 temporarily stops the sheet S and performs a registration roller pair of the registration roller 26 and the registration roller 27 (hereinafter referred to as a registration roller pair) for aligning the toner image and the sheet S. I have. The sheet S conveyed by the pair of feeding and conveying rollers is adjusted in position and timing by the registration roller pair, and then conveyed to the image forming unit 101.

  The image forming unit 101 includes a process cartridge 200 that can be attached to and detached from the image forming apparatus 100 main body (apparatus main body). The process cartridge 200 includes a photosensitive drum 29 serving as an image carrier. In addition, the image forming unit 101 includes a transfer roller 28 disposed to face the photosensitive drum 29. Based on the image information together with the print command, a laser beam is irradiated from the laser scanner unit 104 onto the surface of the photosensitive drum 29 uniformly charged by the charging device, thereby forming an electrostatic latent image on the surface of the photosensitive drum 29. Is done. By developing the electrostatic latent image with the developing device 30, a toner image is formed on the surface of the photosensitive drum 29. The toner image formed on the surface of the photosensitive drum 29 is transferred to the sheet S sent to the nip portion between the photosensitive drum 29 and the transfer roller 28 by the registration roller pair. The sheet S on which the image is transferred is conveyed to the fixing unit 103.

  The fixing unit 103 includes a heating roller 302, a pressure roller 303 in pressure contact with the heating roller 302, a fixing conveyance roller 33, and a fixing conveyance roller 34. The sheet S sent to the fixing unit 103 is guided to a nip portion between the heating roller 302 of the fixing unit 103 and the pressure roller 303 that presses the sheet. At this time, the toner image is heated and pressurized and fixed on the sheet S. Thereafter, the sheet S is carried by a pair of fixing conveyance rollers including a fixing conveyance roller 33 and a fixing conveyance roller 34 and conveyed to the reversing unit 20.

  The reversing unit 20 is a three-roller roller composed of a discharge roller (drive roller) 202, a discharge driven roller (first driven roller) 204, a double-side driven roller (second driven roller) 207, and moves to switch the conveyance path. A possible flapper (switching unit) 210 is included. The triple roller has a function of discharging the sheet S and a function of reversing, and selects a discharge or reversal operation according to a print command. When the sheet S is discharged from the apparatus main body 100, the sheet S is discharged and stacked on the discharge tray 106 as it is. When the sheet S is reversed, the conveyance direction of the sheet S is reversed at a predetermined timing and is sent to the conveyance path for reversal. Thereafter, the sheet S is re-feeded by a double-sided conveyance roller pair including a double-sided conveyance roller 39 and a double-sided conveyance roller 38 provided in the conveyance path for reversal, and a re-feed roller 41 and a re-feed roller 40. Re-feed by roller pair. The re-fed sheet S passes through the image forming unit 101 and the fixing unit 103 again, and is printed on the second side as with the first side. Thereafter, the sheet S printed on the second surface is discharged and stacked on the discharge tray 106 by the reversing unit 20.

(Description of the reversing unit 20 for discharging and reversing the sheet S)
Next, the reversing unit 20 of the image forming apparatus 100 will be described. FIG. 2 is a perspective view of the reversing unit 20. As shown in FIG. 2, the reversing unit 20 includes a discharge frame 201, a discharge roller 202, a discharge roller bearing 203, a discharge driven roller 204, a discharge driven roller holder 205, and a discharge pressure spring (first urging unit) 206. I have. The discharge driven roller 204 is held by a discharge driven roller holder 205 and is urged toward the discharge roller 202 by a discharge pressure spring 206.

  The reversing unit 20 includes a double-side driven roller 207, a double-side driven roller holder 208, and a double-sided pressure spring (second urging unit) 209. The double-side driven roller 207 is held by a double-side driven roller holder 208 and is urged toward the discharge roller 202 by a double-side pressure spring 209. Further, the reversing unit 20 includes a flapper 210 that switches between discharging and conveying paths to both sides, a discharge roller pressing (pressing unit) 211, and a full load detection flag 212.

  Further, as shown in FIG. 2, a fixing unit 103 is provided upstream of the reversing unit 20. The fixing unit 103 includes a fixing frame 301, a heating roller 302, a pressure roller 303, a pressure member 304, a fixing pressure spring 305, a fixing guide 306, a fixing sensor 307, and a fixing double-side guide 308. In addition, the fixing unit 103 includes a fixing gear 309 that transmits driving to the pressure roller 303. Further, the double-sided guide 401 guides the sheet S during reversal.

  Further, the discharge roller 202 rotates when the driving force from the motor M (drive source) that generates the driving force is transmitted from the discharge roller gear 213. The discharge driven roller 204 and the double-side driven roller 207 rotate following the rotation of the discharge roller 202.

  The discharge roller 202 rotates in response to the driving force from the motor M that generates the driving force, and the rotation direction (forward rotation or reverse rotation) is determined according to switching of the drive train by the solenoid 90. FIG. 9 is a block diagram of the first embodiment. As shown in FIG. 9, the CPU 110 is connected to the motor M, the solenoid 90, and the fixing sensor 307. Further, the CPU 110 is connected to a ROM and a RAM, and the CPU 110 executes a program stored in the ROM by using the RAM as a work memory. In the first embodiment, the CPU 110, the ROM, and the RAM constitute a control unit. The control unit switches the drive train that transmits the driving force from the motor M to the discharge roller 202 by controlling the solenoid 90.

  The discharge driven roller 204 is provided below the discharge roller 202 and is pressed against the discharge roller 202 by a discharge pressure spring 206. The discharge driven roller 204 and the discharge roller 202 form a nip portion, and the discharge driven roller 204 rotates following the rotation of the discharge roller 202. When the sheet S is discharged to the discharge tray 106, the discharge driven roller 204 rotates following the discharge roller 202 that rotates forward.

  The double-side driven roller 207 is provided above the discharge roller 202 and is pressed against the discharge roller 202 by a double-side pressure spring 209. The double-side driven roller 207 and the discharge roller 202 form a nip portion, and the double-side driven roller 207 is rotated by the rotation of the discharge roller 202. When the sheet S is conveyed again to the image forming unit 101, the double-side driven roller 207 is rotated by following the discharge roller 202 that rotates in the reverse direction and then rotates in the normal direction.

  FIG. 3 is a cross-sectional view showing the relationship between the forces of the discharge roller 202, the discharge driven roller 204, and the double-side driven roller 207. As shown in FIG. 3, in the cross section perpendicular to the rotation axis direction of the discharge roller 202, the rotation center of the discharge roller 202 is not on a straight line L connecting the rotation center of the discharge driven roller 204 and the rotation center of the double-side driven roller 207. It is provided in the position. A discharge roller press 211 for pressing the discharge roller 202 is provided on the side where the rotation center of the discharge roller 202 is provided with respect to the straight line L (upper left in FIG. 3). That is, the discharge roller press 211 is provided on the opposite side of the straight line L with respect to the rotation center of the discharge roller 202.

  The relationship between the forces of the discharge roller press 211 is as shown in FIG. 3, and the resultant force generated from the discharge driven roller 204 and the double-side driven roller 207 is directed to the discharge roller press 211. That is, the resultant force γ of the double-side driven roller 207 urged in the arrow α direction and the discharge driven roller 204 urged in the arrow β direction acts in the direction of the discharge roller press 211. Therefore, according to the first embodiment, since the discharge roller 202, the discharge driven roller 204, and the double-side driven roller 207 are fixed by the discharge roller press 211 (becomes difficult to shake), it is possible to stably convey the sheet S. .

  The urging force α from the double-side driven roller 207 to the discharge roller 202 is divided into α1 (the same direction as the straight line L) and α2 (the direction perpendicular to the straight line L). Further, the urging force β from the discharge driven roller 204 to the discharge roller 202 is divided into component forces β1 and β2. α1 and β1 and α2 and β2 do not necessarily have the same force. In addition, it is preferable that the rotation center of the discharge roller 202 is arranged so that the angle θ1 formed by the straight lines L and β and the angle θ2 formed by the straight lines L and α are about 5 degrees to 10 degrees.

  FIG. 4 is a perspective view of the reversing unit 20. As shown in FIG. 4, the discharge roller 202 has a rubber roller portion 202 a provided by being divided into a plurality of parts in the rotation axis direction. A sliding holding portion 211 a that is a part of the discharge roller press 211 is provided between the plurality of rubber roller portions 202 a and presses the rotation shaft of the discharge roller 202.

  5 and 6 are cross-sectional views of the reversing unit 20. As shown in FIGS. 5 and 6, in the first embodiment, the discharge roller press 211 constitutes a part of the conveyance guide for guiding the sheet S and detects the full load of the sheet S on the discharge tray 106. The full load detection flag 212 for holding the image is held.

  When the sheet S is discharged to the discharge tray 106, as shown in FIG. 5, the discharge roller 202 rotates clockwise, and the flapper 210 is positioned at the upper part (first position). When the sheet S printed on the first side is reversed to perform double-sided printing, when the fixing sensor 307 detects the leading edge of the sheet S, the solenoid 90 rotates the rotation direction of the discharge roller 202 counterclockwise. In addition to being switched, the flapper 210 moves to a lower position (second position) as shown in FIG.

  FIG. 7 is a cross-sectional view showing the behavior of the sheet S. The sheet S that has passed through the fixing unit 103 is conveyed along the fixing double-side guide 308, and since the flapper 210 is positioned at the lower part, the sheet S is conveyed to the nip between the discharge roller 202 and the double-side driven roller 207 (FIG. 7 (a)). At this time, when the fixing sensor 307 detects that the trailing edge of the sheet S has passed through the fixing double-side guide 308, the rotation direction of the discharge roller 202 is switched clockwise and the flapper 210 is moved to the upper position. Move (FIG. 7B).

  Thereafter, the sheet S is conveyed to the duplex conveyance path by the discharge roller 202 and the duplex driven roller 207. The sheet S conveyed to the duplex conveyance path passes through the image forming unit 101 and the fixing unit 103 again, and is printed on the second surface. As shown in FIG. 7C, the nip between the discharge roller 202 and the discharge driven roller 204 is printed. And is discharged onto the discharge tray 106.

  In the above description of the first embodiment, the configuration in which the present invention is applied to the inverting unit 20 has been described. However, the present invention should not be limited to this. A sheet conveying apparatus using the present invention in a place other than the reversing unit may be used.

  In the above description of the first embodiment, the configuration in which the rotation center of the discharge roller 202 is provided on the downstream side in the discharge direction with respect to the straight line L (upper left side in FIG. 3) has been described. Should not be limited to. In other words, the direction in which the resultant force of the discharge driven roller 204 and the double-side driven roller is generated is the upstream side in the discharge direction (the lower right side in FIG. 3), and the discharge roller 202 that receives the resultant force is pressed by the discharge roller press 211. Good. Note that, from the viewpoint of downsizing the apparatus main body, a configuration in which the discharge roller press 211 is provided on the downstream side in the discharge direction from the straight line L as in the first embodiment is preferable.

  In the above description of the first embodiment, the description has been given of the configuration in which the sliding holding portion 211a of the discharge roller press 211 is disposed between the rubber roller portions 202a (inside in the axial direction). It should not be limited to this. That is, the sliding holding part 211a may be arranged near the outside of the rubber roller part 202a. From the viewpoint of preventing the roller from shaking, a configuration in which the sliding holding portion 211a is disposed between the rubber roller portions 202a as in the first embodiment is preferable. Further, a plurality of sliding holding portions 211 a may be provided in the axial direction of the discharge roller 202.

  FIG. 8 is a view showing a modification of the first embodiment, and is a view seen from the direction of arrow A in FIG. As shown in FIG. 8, according to the present invention, the discharge driven roller 204 and the double-side driven roller 207 are disposed at an angle θ with respect to the discharge roller 202 in the axial direction of the discharge roller 202 (inclined) (horizontal). It may be a configuration.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 20 Inversion part 201 Discharge frame 202 Discharge roller (drive roller)
202a Rubber roller section 203 Discharge roller bearing 204 Discharge driven roller (first driven roller)
205 discharge driven roller holder 206 discharge pressure spring (first urging portion)
207 Double-side driven roller (second driven roller)
208 Double-sided driven roller holder 209 Double-sided pressure spring (second biasing part)
210 Flapper (switching member)
211 Discharge roller presser (presser)
211a Sliding holding part (pressing part)
S sheet

Claims (11)

A driving roller capable of rotating forward and backward by receiving a driving force from a driving source;
A first driven roller that is provided at a position facing the drive roller and rotates following the drive roller;
A second driven roller that is provided at a position facing the drive roller and rotates following the rotation of the drive roller;
A first biasing portion that biases the first driven roller toward the drive roller;
A second urging portion that urges the second driven roller toward the driving roller;
In the cross section perpendicular to the rotation axis direction of the drive roller, the rotation center of the drive roller is provided at a position other than a straight line connecting the rotation center of the first driven roller and the rotation center of the second driven roller. And
The driving is performed so that the driving roller receiving a force from the first driven roller biased by the first biasing portion and the second driven roller biased by the second biasing portion does not move. A sheet conveying apparatus having a pressing portion for pressing a roller. A driving roller capable of rotating forward and backward by receiving a driving force from a driving source;
A first driven roller that is provided at a position facing the drive roller and rotates following the drive roller;
A second driven roller that is provided at a position facing the drive roller and rotates following the rotation of the drive roller;
A first biasing portion that biases the first driven roller toward the drive roller;
A second urging portion that urges the second driven roller toward the driving roller;
A holding portion for holding the drive roller;
In the cross section perpendicular to the rotation axis direction of the drive roller, the rotation center of the drive roller is provided at a position other than a straight line connecting the rotation center of the first driven roller and the rotation center of the second driven roller. The sheet conveying apparatus, wherein the pressing portion is provided on a side opposite to the straight line with respect to a rotation center of the driving roller. The drive roller has a plurality of roller portions in the rotation axis direction,
The sheet conveying device according to claim 1, wherein the pressing portion is disposed between the plurality of roller portions. The drive roller has a plurality of roller portions in the rotation axis direction,
The sheet conveying apparatus according to claim 1, wherein the pressing portion is disposed in the vicinity of the plurality of roller portions.   5. The sheet conveying apparatus according to claim 1, wherein the pressing portion has a function as a conveyance guide that guides a sheet conveyed by the driving roller. 6.   The sheet conveying apparatus according to claim 1, wherein the first driven roller is disposed to be inclined with respect to the driving roller.   Between a first position for guiding the sheet to the nip portion of the driving roller and the first driven roller and a second position for guiding the sheet to the nip portion of the driving roller and the second driven roller. The sheet conveying apparatus according to any one of claims 1 to 6, further comprising a switching member that is movably provided and switches a conveying path.   An angle formed by a straight line connecting the rotation center of the first driven roller and the rotation center of the second driven roller, and a straight line connecting the rotation center of the drive roller and the rotation center of the first driven roller is 5 The sheet conveying device according to any one of claims 1 to 7, wherein the sheet conveying device is at least 10 degrees and at most 10 degrees.   The sheet conveying apparatus according to claim 1, wherein the pressing portion presses a rotation shaft of the driving roller. An image forming unit for forming an image on a sheet;
A sheet conveying device according to any one of claims 1 to 9,
The drive roller and the first driven roller that rotate forward discharge the sheet on which an image has been formed by the image forming unit,
The image forming unit characterized in that the sheet on which the image is formed on the first surface by the image forming unit is conveyed again to the image forming unit by the driving roller and the second driven roller that rotate forward after being reversely rotated. apparatus.   In the cross section perpendicular to the axial direction of the drive roller, the pressing portion is located downstream of the straight line connecting the rotation center of the first driven roller and the rotation center of the second driven roller in the sheet discharge direction. The image forming apparatus according to claim 10, wherein the image forming apparatus is provided.

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